Quote #2

Nor the peaceful farmer any peace, plowing his field or gathering his grain, (6)

Here's a different side of pre-war America: a rural, farming life, where people live in peace, working hard to plow their fields and gather their crops. This peaceful agrarian lifestyle is apparently no longer possible during the Civil War: with a lot of men off fighting, there just weren't enough people to keep things going back on the farm.

Quote #3

Over the traffic of cities—over the rumble of wheels in the streets; (9)

So we've seen the peaceful farmlands, and now we get the hustle and bustle of city life. The traffic and the rumble of wheels suggest that America is a land of industry. But at this point in time, that industry is being overshadowed by the music of war.